Green Roofs

Densely populated Dhaka city offers little space for greenery. As the demand for living space to accommodate the booming population is increasing, green areas around the city are shrinking. As a result, the city is turning into an urban heat island (UHI) and temperatures are on the rise. 

Increasing temperature is a common phenomenon in most urban areas.The sun tends to warm up concrete faster than it does plants and trees, and what is more copious in cities than concrete? Therefore, as summer progresses, the city becomes an unbearable hot-aired place and we use air-conditioning or electric fans that contribute to the heating of outdoor air. The UHI effect can be brought under control by increasing green zones as plants not only help to cool the atmosphere, they also freshen up the air by producing oxygen.
Utilising the space that is available to us seems to be the only way to increase green pockets in the city, and rooftops appear to be a good option for those who are into gardening and have predilection for greenery. Having a green rooftop certainly has its benefits as it helps to reduce temperature and give relief from scorching heat in the summer.
Talking about the benefits of having a rooftop garden, AA Jamal Uddin, a professor at Sher-e-Bangla Agricultural University (SAU), told The Weekend magazine: “The temperature of Dhaka city is usually 4 to 7 degrees higher than nearby settlements.It is because of the dense structural development, and also we are cutting down trees to accommodate the increasing demand for living space. We are using air-conditioners and other electrical cooling machines for our comfort, but that is also a reason for increasing air temperature. Another reason for the rising temperature is the difference between day and night temperatures. The entire city becomes a hotbed during the day and when night falls, the hot surfaces start to cool down, but before that can happen completely, the sun rises again to restart the heating process. In Bangladesh, we are emitting 100,000 to 300,000 metric tons of carbon dioxide every year, which is also adding to the UHI effect. Surface water flow is almost non-existent and airflow is also hampered due to pollution and density of settlements. Nearly 86 percent of our land has been used up and the remaining 14 percent is the area from which we are getting our oxygen, and it is not sufficient to stop the UHI from worsening.”
“Towers for mobile phone communication and our mobile phones are producing electromagnetic radiation, which is detrimental to our health. I once read in an Indian newspaper that green roofs can eliminate this threat by 99.4 percent. Sound pollution from blaring horns from all sorts of vehicles is a terrible problem we face every day, and having plants on the walls, near your window and on rooftops help to deflect and reduce the sound decibel. Plants help remove pollutants from the air and also herbs like tulsi (holy basil) and aloe vera have medicinal benefits. Snake plant, spider plant, peace lily, Boston fern are all good for keeping indoors as well as outdoors as they are beneficial for purifying the air. Lavender, lemongrass and mint plants are known for their mosquito repelling properties, they will help you avoid harmful coils and aerosol sprays,” he added.
About other benefits of having a green space in your house and not just on the rooftop, Jamal Uddin said: “Kids nowadays are always occupied with either an iPad or smart phone, watching videos and cartoons, and then running to the refrigerator for snacks. If you have fruit and vegetable plants on your rooftop or close at hand, such as on green walls, their habit might change. Children really enjoy plucking fruits with their own hands and eating them. It is a healthy hobby that needs to be promoted more and more. While selecting plants for your rooftop garden, a few things must be considered. Firstly, it has to be a dwarf plant and needs to be drought resistant, needs to stay green all year round and produce plenty of fruits, or there is a chance your child might lose interest. Pomegranate, mango, guava, lemon, blood orange, amla, karamcha, jujube, dragon fruit, carambola and water apple are all high yielding, and they are grafted, therefore, they are dwarfs. I prefer fruit and vegetable plants rather than decorative ones, as I am a big believer of the ‘grow what you eat’ concept, and it is certainly healthier.”
On the joys of growing your own plants, Hafiza Rahman, a gardening enthusiast who lives at Rampura Banasree, told this correspondent, “This is my hobby. I love having both decorative and fruit or vegetable plants. I have seen people collecting sarees and ornaments, but I have only one passion and that is gardening, I do not have any other hobby. I buy or collect plants and sometimes they do not survive. There can be many reasons behind that, and I usually hire a gardener who comes in once a week from Evergreen Horticulture to tend to my plants. Not every nursery offers this service since there is a shortage of properly trained gardeners. If a gardener is visiting twice a week, it will cost you Tk3,000 to Tk4,000. I look after my plants myself and have household staff watering them regularly. You have to aerate the soil from time to time, prune dead leaves, and change the soil, maybe once a year in October, and add fertilisers for your plants to thrive. Before winter, I plant tomatoes, and now I will plant okra, bottle gourd, ash gourd, bitter gourd, snake gourd, etc. I plant everything, whether it yields fruit or not. My grandson kept on asking me to plant a banana plant and I did, and the tree has fruits now. I had made concrete trays (for soil) along the sides of my roof to make it less cluttered, but someone told my husband that it would make the top of the building too heavy and there is also risk of damp, so you can see those are mostly empty.”
About compromising the strength of your building with plants on your roof, Jamal Uddin said: “A building is made in such a way that if an entire floor is filled with people standing shoulder to shoulder, it still wouldn’t collapse. The same goes for bridges and flyovers. So, adding some kilogrammes of soil for a few plants should not compromise the strength of your building.” Also, there are soil substitutes available that are lighter than earth.
Apart from having gardens containing potted plants and small grass beds, there are some who have opted for gardens with real soil throughout the entire rooftop. Shantanu Khan’s rooftop in Uttara will give you the feel of walking into a very well organised and clutter-free garden. “Gardening is one of my passions and plants give me a sense of wellbeing and peace. I have been gardening for almost seven years and when I was residing in a duplex home, I had many types of plants such as flowers, fruits and even medicinal ones. We had some rare species of mango trees as well. I like white flowers such as aparajita, and they also smell wonderful. This building is designed with a concept _ it has a vintage look, but it also a minimalist design. You know what they say, less is more and I wanted something plain and simple, so the garden has mainly ferns and it is also in line with the theme of the building.” Khan said.
“I have people coming in from BRAC nursery to tend to my garden every three months, and that is sufficient as I have people at hand to help me out with the garden on a daily basis. Whenever I need assistance, I look it up and consult experts. I wanted a natural and minimalist look and therefore, I have kept it simple and at present I have only two flowering plants. To achieve this, we added 17-inch layers of components, including pie chips, small stones, hollow bricks, geo textile, and finally, soil, which will protect the rest of the building and ensure that my garden thrives. It is incorporated with a spider web like piping system to carry away rain water and avoid damp. This garden keeps the top floor cooler. For those of you interested in rooftop gardening, you should learn all there is to know about the process yourself. Take professional assistance, but knowing things first hand is always better.”
SharminAlam, who lives in Mirpur DOHS, designed her rooftop garden with help from Green Savers. “I started with plants that purify the air such as tulsi, mother-in-law’s tongue, lily, etc as air pollution is a major problem for us. I have tulsi not just on the rooftop, but also planted around the entire building as it helps to keep mosquitoes at bay. I also prefer having a henna plant for its numerous benefits, I also like having lemongrass as well. I had many mint and coriander plants, and they are always at hand in my garden. I have two lemon trees, several tomato plants and a few chilli plants. I went to Sylhet some time ago and threw shatkora (wild orange) seeds in a pot and it was a success, I also have blood orange plants that I grew the same way. I cannot explain the joy of growing what you eat, it is a great feeling. I also distribute among my neighbours and everyone really appreciates it,”she said.
“It is really great to look at as well. I have many flowering plants and nowadays, my friends and I go to Savar and Ashulia for collecting plants. A single bamboo stick with ropes covering it will give a plant support and the jute rope will let the stem stick to it. Bamboo frames will make a plant look bushy and also keep it to the desired size. I enjoy the decorative and fruit yielding plants, but the ones I prefer most are the ones that purify the air. Gardening doesn’t take much of my time or money, I come up here once every day to check and it is pretty affordable. I pay Tk1,100 monthly to Green Savers for gardening services.”
On taking care of your plants and protecting them from diseases, Ahsan Rony, president and founder of Green Savers, an organisation that promotes home gardening, said: “We have an app called Plants Doctor where you will find pictures and descriptions of diseases that are common to plants. We have added all the diseases and solutions we have come across over the past six years in this app, and it is really helpful for gardening enthusiasts. Anyone can call us for our support and we will send our gardener to them and each visit will cost Tk250 to Tk500, depending on the problem. And if anyone is availing our services four times a month, we charge Tk1,100.”
“When I started almost six years ago, the initial cost of setting up a small garden was Tk5,000 to Tk6,000, but now the minimum cost of setting up a garden is Tk25,000 to Tk30,000. We will be launching our ‘plant doctor’ van soon and I am hoping it will encourage more people to take up gardening,” he added.
Recently, the government has takenan initiative to encourage rooftop gardens, offering free gardening services and tax rebates, Khandakar Shariful Alam, a manager at Krishibid Upakaran Nursery, said. “If you contact the Department of Agricultural Extension, they will assist you to design your garden for free and will also give advice on where to buy quality products required for gardening. The Dhaka city corporations and SAU are also involved in the project,” said Alam, whose nursery has been providing gardening services since 1983 and has a large number of clients.
“Since a 10 percent tax rebate was announced (by the mayor of Dhaka South), the number of people interested in rooftop gardening has increased by 30 percent and this is a positive change. But I am not sure whether the rebate is being implemented or not,” he added. 

Photos: Writer